FIG. 14 illustrates a hydraulic excavator 10 including a lower structure 11, an upper structure 12, a cab 13, a work equipment 14, and a power system 15 that includes an engine. The cab 13, the work equipment 14, and the power system 15 are mounted on the upper structure 12, which is rotatably mounted on the lower structure 11. The power system 15 is covered by a top cover 16, side doors 17, and other such components.
Examples of a side door 17 of this type include a double-panel structure comprising an outer panel and an inner panel with an irregular shape formed of raised and recessed portions, wherein the inner panel has a plurality of recessed portions, and the outer panel and the inner panel are affixed to each other by bonding the recessed portions of the inner panel to the outer panel and hemming the peripheral edge of the outer panel (e.g. See Japanese Laid-open Patent Publication No. 9-228412 (pp 2-3, and FIGS. 2-8)).
An example of structures of a door panel developed from such a door panel with a double-panel structure has been proposed. As illustrated in FIG. 15, the derived version of the door panel comprises an outer panel 21 and an inner panel 23 affixed to the inner surface of the outer panel 21. The inner panel 23 has ventilation openings 25, flat adhering portions 27 bonded to the outer panel 21, and a raised portion 29. The ventilation openings 25 are formed by cutting away portions of the inner panel 23. The adhering portions 27 are formed by recessing portions of the inner panel 23. The raised portion 29 is formed so as to bulge away from the outer panel 21. Vertically extending rib portions 31 are formed on the adhering portions 27.
With a conventional door panel with a double-panel structure, the adhering portions 27 of the inner panel 23 are prone to deformation when the outer panel 21 and the adhering portions 27 are bonded together by means of an adhesive. However, the vertically extending rib portions 31 of the developed version of the door panel described above prevent such deformation of the adhering portions 27 and also contribute to increasing the rigidity of the panels, as well as serve as adhesive retaining portions for recovering a surplus of the adhesive. In cases where the door panel were to be modified to withstand severe heat, however, the rib portions 31 interfere with allowing such a modification.
To be more specific, as illustrated in FIG. 16, cutting the portions of the adhering portions 27 where the rib portions 31 are provided results in the formation of holes or the like at the cut surfaces of the adhering portions 27.
In order to solve the above problems, an object of the invention is to provide a door panel that comprises an outer panel and an inner panel joined together at adhering portions and enables formation of large ventilation openings in the adhering portions without significantly impairing the shape or the strength of the door panel, regardless of whether rib portions are formed on the adhering portions in order to prevent deformation of the adhering portions or for other purpose.